I've been talking for a while about knowledge gardening, as it applies to running wikis, large community sites, or other interactive, collaborative knowledge stores. I really like the metaphor -- it implies a fertile ground for organic systems to grow, but also a gardener to take care of the weeds that inevitably grow. Translation: you need a site mom/gardener/etc. to get the most out of your shared space.
Tagging is new to the party, and we're still figuring out how to use it. Jordan Willms (as well as creating lots of great Drupal code) has been thinking a lot about mixing tags with a little more control: gardened hierarchical folksonomy. Follow the link to check out his ground rules:
What I propose is a concept called 'gardened hierarchical folksonomy'. The basic idea is that you let the site visitors build and construct the taxonomy tree. While this sounds like pure anarchy, it can be effectively controlled with a few ground rules:stream of conscious: gardened hierarchical folksonomy - the next evolution in semantic classification
Update: WordPress is appointing Bug Gardeners. Pretty much the same thing, except I don't know if a bug or knowledge is the easier thing to garden :P
Over at 43 Places, the Robots have been dealing with something very similar as they try to help people organize all the worlds places -- a hierarchy of pre-made places with users iterating over and filling in the gaps, and then going back and fixing mistakes and making adjustments.